I guess it depends on what you have access to, and what you prefer. Honestly, if you don't have access to weights or machines or anything, honest-to-God push-ups are one of the best workouts to do. There are a lot of variations of the standard push-up, too, like the wide push-up (with your hands farther apart than shoulder-width), that can really help.
As far as other stuff, I've become pretty fond of tube flies and wide and lopsided push-ups for warm-up, standing cable flies, flat bench dumbbell presses, and inclined and declined barbell presses. Those are all pretty basic techniques, but to get them all down is to cover pretty much all the bases. You'll have to judge yourself how capable you are of doing them all - assuming you're doing other stuff, too - in a single session; I often find that I have to break it up either doing abs or biceps or something somewhere in the middle, or do half of them one night, half another. It just depends on you.
There are a lot of people on this forums more qualified - by their pics,
- to answer this than I, but I hope this helps at least get you started!